Diffchecker logoDiffchecker
PrivateSecureFree

Diff Checker
Compare Two Texts Online

Free online diff checker to compare two texts, find differences between files, and merge changes instantly. This browser-based text difference checker handles plain text, source code, configuration files, and logs. Character-level highlighting catches edits that a line-by-line diff tool misses.

Your text never leaves the browser tab. The comparison runs locally on your device, the Share link carries both versions inside the URL itself, and nothing is ever stored on a server. It handles files up to 25,000 lines per side and keeps working even if you go offline.

Character-Level Text Difference Checker

Most online diff checkers stop at the line level. Ours goes further: when two lines differ only partially, it runs a second pass that highlights the exact characters that changed. That's the difference between knowing a line is wrong and knowing which three characters are wrong. Exactly what matters when you compare text online for code reviews, typo hunts, or config audits.

Original
Changed
const config = {
timeout: 3000,
retries: 3,
env: "development"
}
const config = {
timeout: 5000,
retries: 5,
env: "production"
}
+3 changed-3 removedCharacter-level highlighting

Compare Large Text Files Online

Compare two text files with 25,000+ lines without scrolling past thousands of identical rows. This large file diff checker collapses unchanged regions by default so the differences land at the top of the page. Click any collapsed block to expand surrounding context. Useful for reviewing configuration files, database exports, generated code, and long log excerpts.

return users.filter(u => u.active);
const limit = 10;
const limit = 25;
return results.slice(0, limit);
Expand 47 unchanged lines
// ... validation logic ...
if (!user.email) throw new Error();
const normalized = user.name.trim();
await db.users.update(user.id, data);
logger.info("debug");
logger.info("production");
}

Split View And Unified Diff View

Choose the layout that suits the file. Split view puts the original and changed text in two columns, best for longer texts and wider screens. Unified view interleaves both versions in a single column, closer to what git diff prints, and better for narrow screens and quick reviews. Switch between them at any time without recomputing the diff.

Split view
import React;
const App = () =>
<Main />
import React;
const Dashboard = () =>
<Main />

Side by side. Best for reviewing longer texts on wide screens.

Unified view
import React;
const App = () =>
const Dashboard = () =>
<Main />

Inline changes in a single column. Great for quick reviews and narrow screens.

Compare And Merge Text Files

Find differences between two texts and merge them on your terms. Every change has Accept and Reject buttons. Step through the diff to build the exact version you want, then copy or download the merged output. Useful for combining code changes, reconciling two drafts, or producing a clean final from two revisions.

Merge2 accepted1 rejected
Original
Changed
Action
Result
const api = {
const api = {
const api = {
url: "/v1"
url: "/v2"
url: "/v2"
timeout: 3000
timeout: 500
timeout: 3000 kept original
retry: false
retry: true
retry: true

How To Compare Two Texts Online

Three steps, no sign-up, results in milliseconds. This is all it takes to check diff online and find every difference between your texts.

01

Paste Original Text

Drop your original text, code, or file contents into the left editor. You can paste from clipboard, upload a file, or type directly. Syntax highlighting turns on automatically for common languages.

02

Paste Changed Text

Enter the modified version in the right editor. Differences are highlighted as you type: red for deletions, green for additions, with character-level precision on partially changed lines.

03

Merge And Export

Use the merge tool to accept or reject individual changes, then copy the merged result or download it as a file. Share the full comparison via a URL that encodes the text directly, with no server storage involved.

The Best Online Text Compare Tool

A compare text online tool that doesn't upload your data, doesn't gate features behind a login, and doesn't make you wait for a server round-trip on every keystroke.

Instant Text Diff

Compare text online in real time with a Myers-style diff algorithm. Differences update on every keystroke. No Compare button, no processing delay.

100% Private And Secure

Your text never leaves the browser tab. Unlike diff tools that upload to a server, this online text diff checker runs entirely client-side with no API call for the comparison.

Smart Merge Tool

Find differences between two texts and merge them with per-hunk Accept and Reject controls. Export the merged result as a text file or copy to clipboard.

Large File Diff Checker

Compare two text files with 25,000+ lines efficiently. Unchanged sections collapse by default so you focus on what actually changed.

Secure URL Sharing

Share your diff online through a self-contained link. Both sides of the comparison are encoded directly in the URL fragment, with nothing stored on any database.

Works Offline

This text comparator keeps working once the page is loaded, even with the network disconnected. Useful on flights and in restricted environments.

Split And Unified Views

Side-by-side split diff for wide screens, unified diff for narrow ones. Toggle without losing scroll position.

Syntax Highlighting

CodeMirror-powered editors with language modes for JavaScript, TypeScript, Python, JSON, SQL, YAML, HTML, CSS, and many more.

No Sign-Up Required

Start comparing immediately. No registration, no email, no account. This diffchecker free tool is open to personal and commercial use without restriction.

What This Text Comparison Tool Handles

This online diff checker is format-agnostic. If it's text, you can compare it. These are the patterns that show up most often in real use.

Code Diff Checker

A code diff checker for any programming language. Character-level highlighting makes it ideal for code reviews, debugging, and reconciling diverged branches before you push.

  • JavaScript, TypeScript, Python
  • Java, C++, C#, Go, Rust
  • HTML, CSS, SCSS, LESS
  • SQL schema and query diffs
  • Shell scripts and Dockerfiles

Text Compare Tool

A text comparator for written content. Spot revisions between drafts without wading through Word's Track Changes. Paste, compare, done.

  • Article and blog revisions
  • Resume and CV edits
  • Contract and policy redlines
  • Email and proposal drafts
  • Translated drafts vs. source

File Diff Checker

A file difference checker for structured and semi-structured text. All the formats that live in your repo and your /etc directory, diffed without a parser getting in the way.

  • XML, JSON, YAML, TOML configs
  • .env files across environments
  • CSV exports and data dumps
  • Kubernetes and Helm manifests
  • Log file analysis

Frequently Asked Questions

What is a diff checker?

A diff checker, also called a text difference checker or text comparator, is a tool that compares two texts and highlights what's different between them. It shows additions, deletions, and modifications so you can see exactly what changed. This free online diff checker does both line-level and character-level comparison.

How do I compare two texts online?

Paste your original text in the left panel and the changed text in the right panel. This text difference checker instantly highlights every difference: red backgrounds mark removed content, green marks additions, and the exact characters that changed are emphasized inside each modified line.

What's the difference between two texts?

The difference between two texts is any addition, deletion, or modification from one version to the other. This diff checker finds every difference automatically: it marks removed lines in red, added lines in green, and highlights the exact characters that changed on partially modified lines. No manual reading required.

Is this online diff checker free?

Yes. This diff checker is 100% free for both personal and commercial use. No sign-ups, no usage limits, no hidden fees, no premium tiers, and no feature gating.

Is my data secure?

Yes. The diff algorithm runs in the browser tab's JavaScript runtime, not on a server. No POST request is made with the text you paste, and the Share feature encodes both sides into the URL fragment (the part after the #), which browsers never send to servers. You can audit this yourself in DevTools' Network panel.

Can I use this as a code diff checker?

Yes. This tool works as a code diff checker for any programming language: JavaScript, TypeScript, Python, Java, C, C++, Go, Rust, HTML, CSS, SQL, and more. Syntax highlighting is automatic for common languages and can be forced from the editor controls.

Does this file diff checker support large files?

Yes. This file difference checker efficiently handles files with 25,000+ lines per side. Unchanged regions collapse automatically so you focus on the differences. The underlying diff has no hard cap; practical limits come from editor scrolling on your device.

What diff algorithm is under the hood?

A Myers-based line diff with a character-level secondary pass on partially changed lines. The output is close to what git diff produces, plus the inline character highlighting that plain git doesn't show.

How does the merge feature work?

After comparing texts, each change has Accept and Reject buttons. Step through the diff to pick which version to keep for each hunk. The Result column assembles the merged text as you go. Copy or download the result when you're done.

Can I share my diff comparison with others?

Yes. Click Share to generate a self-contained URL. Both sides of the comparison are encoded directly in the link. Nothing is stored on a server, the link never expires, and anyone with it sees the same diff you do.

Does this diff checker work offline?

Yes, once the page has loaded. The editors, the diff engine, and the merge tool are all client-side, so subsequent visits work with the network off. Useful on planes and in locked-down environments.

What's the difference between split and unified view?

Split view shows the original and changed text side by side in two columns, easier to read on wide screens and for long files. Unified view interleaves both versions in a single column with inline changes, better for narrow screens and for quick review, similar to git diff output.

Start Comparing Text Online - Free

Scroll up and paste your texts. No sign-up, no downloads, no limits.